Luminosity distance uncertainties from gravitational wave detections of binary neutron stars by third generation observatories

A new generation of terrestrial gravitational wave detectors is currently being planned for the next decade, and it is expected to detect most of the coalescences of compact objects in the Universe with masses up to a thousand times the solar mass. Among the several possible applications of current and future detections, we focus on the impact to the measure of the luminosity distance of the sources, which is an invaluable tool for constraining the cosmic expansion history of the Universe. We study two specific detector topologies, triangular and L-shaped, by investigating how the topology and relative orientation of up to three detectors can minimize the uncertainty measure of the luminosity distance. While the precision of the distance measurement is correlated with several geometric angles determining the source position and orientation, focusing on the bright standard sirens and assuming a redshift to be measured with high accuracy, we obtain analytic and numerical results for its uncertainty, depending on the type and number of detectors composing a network, as well as on the inclination angle of the binary plane with respect to the wave propagation direction. We also analyze the best relative location and orientation of two third generation detectors to minimize the luminosity distance uncertainty, showing that prior knowledge of the inclination angle distribution plays an important role in the precision recovery of luminosity distance and that a suitably arranged network of detectors can drastically reduce the uncertainty measure, approaching the limit imposed by lensing effects intervening between source and detector at a redshift z≳0.7.